1. Technical Field
The present invention is directed to filters for use in air filtration units.
2. Background Art
The present invention finds predominant use in the field of air filtration units. The term, air filtration unit, includes devices such as air extractor hoods typically found in commercial food premises, various air extraction devices and such like, and may extend to air conditioning units. The primary consideration is where there is an airflow to be filtered.
The air filtration elements which are traditionally used are generally constructed of a reusable material able to be cleaned or reconditioned. Traditional exhaust filter elements generally comprise metal mesh or honeycomb material supported by a frame. More recently, flame baffle filters have gained acceptance.
When filtering air in a food preparation environment, air laden with greasy cooking vapour, is drawn through the filters by fan assistance. The greasy droplets are trapped by the filters and the "purified" air passes through ducting to be released into the environment outside the building. In the process, the interior of the hood, fan and ducting become progressively and often quickly contaminated and greasy.
The build up of contaminants in the ducting constitutes a significant fire hazard.
The filter elements often become quickly soiled depending upon conditions of use and require regular cleaning to maintain an efficient filtering action to provide, e.g. clean air in the workplace. If left for a prolonged period, severe clogging of the filter element may occur, reducing airflow, filtering performance and creating unpleasant working conditions.
Badly soiled filters can also release trapped contaminants onto food and food processing surfaces beneath the air filter.
Cleaning filter elements is messy, often inconvenient and deposits may be difficult to remove, requiring quite harsh chemicals. Cleaning the hood interior, fan and ducting is even more difficult because of restricted access.
In larger population centres, specialist service companies are often employed to remove soiled elements by roster and to then fit clean replacements, (sometimes unnecessarily), otherwise staff or proprietors must attempt the work themselves.
The continuing rapid growth of the fast food industry in which deep fat frying methods are often employed, ensures that the extent of the problems associated with exhaust hoods, metal filters and contaminated flues are similarly multiplying.
There are therefore, difficulties involved with the use of filter elements commonly in use, arising from the neglect of their cleaning. This neglect is usually an indirect consequence of the difficulties associated with cleaning or can simply arise from a desire to keep costs down.